Question: Solve for $x$ and $y$ using substitution. ${x-4y = -3}$ ${y = -2x+3}$
Explanation: Since $y$ has already been solved for, substitute $-2x+3$ for $y$ in the first equation. ${x - 4}{(-2x+3)}{= -3}$ Simplify and solve for $x$ $x+8x - 12 = -3$ $9x-12 = -3$ $9x-12{+12} = -3{+12}$ $9x = 9$ $\dfrac{9x}{{9}} = \dfrac{9}{{9}}$ ${x = 1}$ Now that you know ${x = 1}$ , plug it back into $\thinspace {y = -2x+3}\thinspace$ to find $y$ ${y = -2}{(1)}{ + 3}$ $y = -2 + 3$ $y = 1$ You can also plug ${x = 1}$ into $\thinspace {x-4y = -3}\thinspace$ and get the same answer for $y$ : ${(1)}{ - 4y = -3}$ ${y = 1}$